WO2013153622A1

WO2013153622A1 - Display device and display characteristic correction method

Info

Publication number: WO2013153622A1
Application number: PCT/JP2012/059802
Authority: WO
Inventors: 阿部　正敏
Original assignee: Ｎｅｃディスプレイソリューションズ株式会社
Priority date: 2012-04-10
Filing date: 2012-04-10
Publication date: 2013-10-17
Also published as: JP5904614B2; CN104205201A; JPWO2013153622A1; CN104205201B; US9741294B2; US20150054806A1

Abstract

The display device is provided with: a display panel (2) that displays an image; an optical sensor (5), which is disposed facing the display surface of the display panel (2) and measures the radiation value of the light emitted by the display panel (2) as a measured optical value; a measured value-revising unit (1), which revises a revision target measured optical value that is a measured optical value to be revised using a function that represents the amount of change in the measured optical value per unit time and outputs same as a revised measured optical value; and a signal processing unit (4), which generates from the revised measured optical value a control value for controlling the display panel (2) to stabilize the display quality of the image displayed on the display panel (2) and generates a post-processing video signal that displays an image from the control value and an input video signal supplied from an external device. The function represents the change in the radiation value, when measuring the revision target measured optical value, during a disabled period in which the signal-processing unit (4) disables the stabilizing function that keeps the radiation value of the light source (3) of the display panel (2) constant.

Description

Display device and display characteristic calibration method

The present invention relates to a display device (liquid crystal monitor, projector, etc.) and a display characteristic calibration method.

In recent years, liquid crystal display devices that display an image on a display panel using a backlight are widely used in various industrial fields. For example, FPD (Flat Panel Display) that displays a video signal supplied from the outside of a liquid crystal display device on a display panel using liquid crystal is widely used. In such a liquid crystal display device, light is radiated to a display panel using a liquid crystal element and a display panel such as an ultra-high pressure mercury lamp, a W / RGB LED (Light Emitting Diode), a cold cathode tube (CCFL: Cold Cathode Fluorescent Lamp). And an optical member of a backlight (light source, BL: Back Light) for irradiation. In addition, the display device includes, as circuit units, a BL driving unit that controls the luminance of light emitted from the backlight, and a circuit that drives the display panel.

When the display device described above is used as a display device for graphic design or medical use, the display characteristics (stability of color display) specified in advance are maintained over a long period of time, and the display device can always be used in a stable state. It is required to be quality.
When maintaining this stable state, an optical sensor such as a brightness sensor or a color sensor is provided on the display surface of the display panel, and the brightness and color are measured. There is a display device that stabilizes quality (see, for example, Patent Document 1). When an optical sensor is provided on the display surface of the display panel, not only the luminance value but also the displayed color and the gamma (γ) characteristic of the display panel can be measured in order to maintain display quality.
On the other hand, there is a display device in which an optical sensor or the like is provided not on the display surface of the display panel but on the back surface, and the display quality is stabilized by this measured value. For example, when the display device is a liquid crystal display device, if an optical sensor is provided on the back of the liquid crystal panel (display panel), the brightness of the light emitted from the backlight to the liquid crystal panel is measured, and the brightness of the emitted light is stabilized. Turn into.
Therefore, the method of providing the optical sensor on the display surface of the display panel is superior in that the display quality can be stabilized more than the method of providing the optical sensor on the back surface of the display panel.

Next, FIG. 6 is a diagram illustrating a configuration example of the liquid crystal display device 200 in the method in which the optical sensor is provided on the back surface of the display panel described above.
The optical sensor 205 measures the luminance of the light that the backlight 3 irradiates the back surface of the display panel 2 and outputs the measurement result to the signal processing unit 204 as an optical measurement value.
The signal processing unit 204 converts the gradation of the input video signal input from the external device into a post-processing video signal that drives the display element of the display panel 2 based on the optical measurement value supplied from the optical sensor 205, and displays it. Output to panel 2. Further, the signal processing unit 204 sets the luminance value of the light emitted from the backlight 3 to a set luminance value set in the internal storage unit in advance, that is, the luminance value of the irradiated light is constant even when the temperature changes. Is generated, and the backlight 3 is controlled by this drive signal.

Next, FIG. 7 is a diagram illustrating a configuration example of the liquid crystal display device 300 in a system in which an optical sensor is provided on the display surface of the display panel described above.
When the optical sensor 5 is, for example, a luminance sensor, the luminance of the light emitted from the measurement area 21 of the display panel 2 and emitted from the backlight 3 to the display panel 2 is measured, and the measurement result is optically measured. The value is output to the signal processing unit 304.
The signal processing unit 304 converts the gradation of the input video signal input from the external device into a post-processing video signal that drives the display element of the display panel 2 based on the optical measurement value supplied from the optical sensor 5, and displays it. Output to panel 2. Further, the signal processing unit 304 irradiates even if the luminance value of the light emitted from the backlight 3 that passes through the measurement region 21 becomes a set luminance value preset in the internal storage unit, that is, the temperature changes. A drive signal with a constant light luminance value is generated, and the backlight 3 is controlled by this drive signal.

At this time, the signal processing unit 304 measures the black luminance and the white luminance, and obtains the drive signal and the processed video signal for the backlight 3 so that the dynamic range becomes a preset numerical value. That is, the aperture of the display element in the measurement region 21 can be controlled, and the luminance value corresponding to the aperture transmitted from the measurement region 21 can be measured. As described above, not only the white luminance but also the black luminance or the gamma characteristic can be measured. It is possible to measure the luminance values of a plurality of halftones (gradation between white luminance and black luminance) to be obtained.

In the liquid crystal display device of FIG. 7 described above, in cases other than the measurement for stabilizing the display quality in which the luminance value of the light emitted from the display panel 2 is constant, for example, color measurement, gamma characteristic measurement, black luminance and halftone When the luminance value is measured, the signal processing unit 204 needs to disable the luminance stabilization function. In general, the luminance stabilizing function displays white in the measurement region 21, measures the white luminance, and controls the luminance value of the light emitted from the backlight 3 so that the luminance value becomes constant. That is, the luminance stabilization function controls the drive signal that drives the backlight 3 so that the luminance value of white luminance becomes a preset setting value.

For this reason, when performing measurements other than white luminance, if the luminance value is not measured in a state where the luminance stabilization function is disabled, for example, when the luminance value of black luminance is measured, the signal processing unit 304 performs this black luminance measurement. Is read as a white luminance value. The signal processing unit 304 controls the backlight 3 and the display panel 2 so as to obtain a preset setting value, that is, the luminance value of white luminance, corresponding to the luminance value of black luminance. The luminance value of the light transmitted from 2 is not correctly controlled.
Therefore, when measuring a brightness value other than white brightness, the above-described brightness stabilization function is disabled and the measurement process is performed.

However, when the luminance stabilization function is disabled, the color measurement, the gamma characteristic measurement, the black luminance and the halftone luminance value are measured without controlling the luminance value of the light emitted from the backlight 3. become. After the signal processing unit 304 finishes the process for stabilizing the display quality, that is, the signal processing unit 304 performs color measurement, gamma characteristic measurement, black luminance and halftone luminance value measurement. After the completion, the brightness stabilization function is enabled, and the mode is changed from the measurement mode for performing optical measurement of display quality to the normal mode for performing normal image display.

At this time, if the luminance stabilization function is disabled, the luminance value of the light transmitted through the display panel 2 may change. For example, when the CCFL is used for the backlight 3, the light emission efficiency of the CCFL changes depending on the temperature. Therefore, when the lighting time is long, the temperature rises and the luminance value of the light applied to the display panel 2 changes. Become.
Next, FIG. 8 is a diagram for explaining the luminance value of the light irradiated by the backlight 3. In FIG. 8, for example, when the luminance value of the light emitted from the backlight 3 is stable over time, the luminance value L0 measured at time T0 and the luminance value L1 ′ measured at time T1 are as follows. Will be equal. However, when the luminance value of the light emitted from the backlight 3 changes with time, the luminance value L0 measured at time T0 is not equal to the luminance value L1 measured at time T1.

Therefore, when the luminance stability function is disabled and the luminance values such as the gamma characteristic, the halftone, and the black luminance are measured, the luminance value of the light that the backlight 3 irradiates the display panel 2 changes. The brightness value varies depending on the measurement time. That is, when measuring the optical measurement value for stabilizing the display quality, the video signal having the same gradation is given to the display panel 2 and measured at different times, the control values have the same gradation. However, a luminance value that varies from time to time is measured as an optical measurement value. For this reason, the optical measurement value measured for use in adjusting the setting value that controls the display quality when the brightness stabilization function is enabled is measured as a value that deviates from the state where the brightness stabilization function is enabled at each time. Will be. This disables the brightness stabilization function, and then uses each of the optical measurement values measured at different times and compares them to make image quality control settings that enable image quality control with the brightness stabilization function enabled. Will be adjusted. Therefore, stabilization processing of display quality when the luminance stabilization function is enabled, which is performed using image quality control setting values adjusted by optical measurement values each having a different shift amount with respect to the state where the luminance stabilization function is enabled Is less accurate.
Therefore, in the configuration of the liquid crystal display device 300 in which the optical sensor is provided on the display surface of the display panel, the user who needs the accuracy of the display image quality and the stability of the display quality can only control the low-quality display quality. There will be no.

JP 2008-102490 A

The problem to be solved is that in a liquid crystal display device in which an optical sensor is provided on the display surface of the display panel, the luminance value corresponding to the gradation is measured under various conditions in order to adjust the image quality control setting value. Therefore, when the luminance stability function is disabled and color measurement, gamma characteristic measurement, black luminance or halftone luminance value measurement is performed, the luminance value changes depending on the measurement time, and the luminance stabilization function is activated. The optical measurement value corresponding to the luminance value of the backlight in the state cannot be obtained, and the display quality with high display quality cannot be controlled.

The display device of the present invention includes a display panel that displays an image, an optical sensor that is disposed opposite to the display surface of the display panel, and that measures the amount of light emitted from the display panel as an optical measurement value, A corrected optical measurement value, which is an optical measurement value to be corrected, is corrected by a function indicating a change amount of the optical measurement value per unit time, and output as a corrected optical measurement value; and the display panel A control value for controlling the display panel, which stabilizes the display quality of the displayed image, is generated from the corrected optical measurement value, and the image is obtained from the control value and an input video signal supplied from an external device. A signal processing unit that generates a processed video signal to be displayed, and when the function measures the correction target optical measurement value, the signal processing unit makes the irradiation amount of the light source of the front display panel constant. Characterized by exhibiting a change in the irradiation amount in the inactive period has disabled the ability.

In the display device of the present invention, the measurement value correction unit includes a timer unit for counting time, a plurality of reference optical measurement values measured at different times including a start time at which the invalid period is started, and the reference optical measurement. A coefficient calculation unit that obtains a function indicating the relationship between each value and the time measured by the timer unit; and when the correction optical measurement value is obtained from the correction target optical measurement value, the correction target optical measurement value is calculated from the function. Obtain an estimated reference optical measurement value at the measured time, divide the reference optical measurement value at the start time by the estimated reference optical measurement value, use the division result as a change ratio, and multiply the correction target optical measurement value by the change ratio And a correction calculation unit that uses the result of multiplication as a corrected optical measurement value.

In the display device according to the aspect of the invention, the coefficient calculation unit may include a first reference optical measurement value that is an optical measurement value measured at a first time that is the start time counted by the timer, and the first count that is counted by the timer. A difference from a second reference optical measurement value, which is an optical measurement value measured at a second time after one time, is obtained, and the difference is subtracted by the time width of the difference between the first time and the second time. An optical measurement value change amount per time is calculated, the optical measurement value change amount is multiplied by a time variable, a linear function is obtained by adding the first reference optical measurement value to the multiplication result, and the linear function Is the function.

In the display device of the present invention, the coefficient calculation unit obtains a spline curve from a plurality of reference optical measurement values measured at different times including the reference optical measurement value measured at the start time, and the spline curve is It is a function.

The display device of the present invention is characterized in that a luminance value measured as the reference optical measurement value is white luminance.

The display device of the present invention is characterized in that the optical measurement value to be corrected is a luminance value in each of black luminance, gamma characteristic, and color measurement.

The display characteristic calibration method of the present invention includes a process of measuring a luminance value of light emitted from the display panel by an optical sensor as an optical measurement value, which is disposed opposite to a display surface of a display panel of a liquid crystal display device, A measurement value correction process in which a value correction unit corrects an optical measurement value to be corrected, which is an optical measurement value to be corrected, with a function indicating a change amount of the optical measurement value per unit time, and outputs the corrected optical measurement value as a corrected optical measurement value; The signal processing unit generates a control value for controlling the liquid crystal panel, which stabilizes the display quality of the image displayed on the display panel, based on the corrected optical measurement value, and is supplied from the control value and an external device. And a signal processing step of generating a processed video signal for displaying an image on the display panel from the input video signal, wherein the function measures the signal when the correction target optical measurement value is measured. Characterized in that indicating the change of the luminance value in disabled periods processing section is a luminance value of the light source before the display panel to disable the luminance stability functions constant.

In a liquid crystal display device having a configuration in which an optical sensor is provided on a display surface of a display panel, the display device of the present invention adjusts an image quality control setting value and measures a luminance value corresponding to a gradation level under various conditions. When the brightness stability function is disabled, color measurement, gamma characteristic measurement, black brightness or halftone brightness value measurement is performed, even if the brightness value changes depending on the time of measurement, the brightness stabilization function is activated. Thus, an optical measurement value corresponding to the luminance value of the backlight in the present state can be obtained, and display quality can be controlled with high accuracy.

It is a block diagram which shows the structural example of the display apparatus 100 by one Embodiment of this invention apparatus. It is a block diagram which shows the structural example of the measured value correction | amendment part 1 in FIG. It is a graph which shows the linear function which the coefficient calculating part 12 in this embodiment produced | generated. It is a graph explaining the process which calculates an estimated optical measurement value sequentially from the linear function which the coefficient calculating part 12 in this embodiment produced | generated. It is a graph explaining the process which calculates the correction | amendment optical measurement value using the 3rd reference | standard measurement value of a 1st reference | standard measurement value, a 2nd reference | standard measurement value, and a 3rd reference | standard measurement value. It is a figure which shows the structural example of the liquid crystal display device in the system which provides an optical sensor in the back surface of a display panel. It is a figure which shows the structural example of the liquid crystal display device in the system which provides an optical sensor in the display surface of a display panel. It is a figure explaining the luminance value of the light which the backlight 3 irradiates.

The present invention disables the luminance stabilization function when adjusting the image quality control setting value for maintaining the display quality of the display device according to the surrounding environment and the change in the light source of the display device, and optical measurement used for this adjustment. The value is acquired by an optical sensor provided facing the display surface of the display panel. In the present invention, the optical measurement value measured by the optical sensor is corrected by a function obtained from the reference optical measurement value measured at different times, and used as a corrected optical measurement value for adjustment.

As a result, the present invention invalidates the luminance stabilization function, and therefore, the deviation from the optical measurement value measured when the luminance stability function is valid is caused by the change in the luminance value irradiated by the light source of the display device that changes with time. to correct.
Here, the image quality control setting value for maintaining the display quality is, for example, the ratio of each RGB gradation when displaying each color, the correspondence between the maximum RGB gradation and the maximum luminance value, or the gamma characteristic. A set value group including a control value for adjusting each of the gamma curves used for correction.

Hereinafter, a display device and a display characteristic calibration method according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration example of a display device 100 according to an embodiment of the device of the present invention. In the present embodiment, a liquid crystal display device having the display panel 2 that is a liquid crystal panel in which a plurality of liquid crystal elements are arranged in a matrix will be described as an example of the display device 100. However, when the luminance stabilization function is disabled, The present invention can be applied to any display device as long as the luminance value irradiated by the light source of the display device changes with the passage of time or the display panel includes a device whose display characteristics change with the passage of time.
In FIG. 1, the display device 100 includes a measurement value correction unit 1, a display panel 2, a backlight 3, a signal processing unit 4, and an optical sensor 5. Here, the signal processing unit 4 performs the same operation as the signal processing unit 304 shown in FIG. Hereinafter, the description of the signal processing unit 4 will be made only on parts different from the signal processing unit 304.

The backlight 3 is provided to face the back surface of the display panel 2 and irradiates the back surface of the display panel 2 with light.
The optical sensor 5 measures the luminance value of the emitted light emitted from the measurement region 21 of the display panel 2 when the light irradiated on the back surface of the display panel 2 is transmitted through the display element of the display panel 2, and the measured luminance value. Is output to the measurement value correction unit 1 as an optical measurement value.

When the adjustment start signal (described later) for invalidating the luminance stabilization function is not supplied from the signal processing unit 4, that is, when the luminance stabilization function is valid, the measurement value correction unit 1 outputs the optical measurement value from the optical sensor 5. Output as corrected optical measurement value without correction. In addition, when the adjustment start signal is supplied from the signal processing unit 4, that is, when the luminance stabilization function is invalid, the measurement value correcting unit 1 receives a signal indicating that the adjustment processing has ended from the signal processing unit 4. Until supplied, the optical measurement value from the optical sensor 5 is corrected and output as a corrected optical measurement value.

The signal processing unit 4 outputs an adjustment start signal to the measurement value correcting unit 1 when adjusting the image quality control setting value set inside. Further, the signal processing unit 4 invalidates its own luminance stabilization function and starts an invalid period of the luminance stabilization function. Thereby, the signal processing unit 4 stops the process of controlling the brightness of the backlight 3 to be constant as a preset brightness value corresponding to the brightness value supplied from the optical sensor 5. For this reason, when the backlight 3 is a CCFL, the luminance value increases with time as shown in FIG.

Then, after invalidating the luminance stabilization function, the signal processing unit 4 outputs a timing signal indicating the timing for acquiring the optical measurement value used for adjusting the image quality control setting value to the measurement value correction unit 1. In addition, the signal processing unit 4 outputs a timing signal for acquiring all optical measurement values necessary for adjusting the image quality control setting value, and then transmits an adjustment end signal to the measurement value correction unit 1 to set the image quality control setting. Requests transmission of corrected optical measurements required for value adjustment. Then, the signal processing unit 4 ends the ineffective period of the luminance stabilization function after the elapse of a predetermined time set in advance, and validates the luminance stabilization function.

Here, when the signal processing unit 4 outputs the adjustment start signal, the adjustment end signal, and the timing signal, the signal processing unit 4 is in a state of a measurement optical value to be measured corresponding to the adjustment start signal, the adjustment end signal, and the timing signal. It controls its own internal circuit. For example, when a reference optical measurement value (described later) used in the measurement value correction unit 1 is a luminance value of white luminance, when transmitting an adjustment start signal and an adjustment end signal described later, the display panel 2 has a white luminance value. The liquid crystal element in the measurement region 21 is controlled. That is, the signal processing unit 4 displays a video signal for controlling the liquid crystal element so that the luminance value of the light emitted through the liquid crystal element in the measurement region 21 becomes an aperture value that becomes a luminance value of white luminance. To supply. For example, if the display panel 2 is a color liquid crystal panel, the signal processing unit 4 maximizes all of the RGB gradations and maximizes the aperture of the liquid crystal elements with respect to the liquid crystal elements in the measurement region 21. To do.

Further, for example, when it is desired to use the luminance value at the black luminance as the optical measurement value, when transmitting the timing signal, the signal processing unit 4 has the lowest gradation for all the liquid crystal elements in the measurement region 21 of the display panel 2. A gray scale signal is supplied to minimize the aperture of the liquid crystal element and to achieve black luminance.

Further, for example, when the optical sensor 5 is a color sensor having three channels of RGB and performs color measurement, when the user determines a combination of RGB gradations set in advance by the user and transmits a timing signal, this gradation degree is used. The control signal of the combination is supplied to the display panel 2. Then, the signal processing unit 4 causes the measurement region 21 of the display panel 2 to display a color based on the combination of gradations on the measurement region 21. Here, the signal processing unit 4 determines whether or not the optical measurement values of the respective RGB channels acquired from the optical sensor 5 correspond to the measurement values set corresponding to the gradation levels of the preset RGB combinations. Thus, processing for adjusting the set value of the gradation when expressing the color is performed.

Further, for example, when adjusting the gamma curve, the signal processing unit 4 sequentially converts the gradation of the input video signal linearly when converting the input video signal into a processed video signal for controlling the liquid crystal elements of the display panel 2. Every time the timing signal is output to the measurement value correction unit 1, the increased control signal of the liquid crystal element is given to the display panel 2 without being corrected by the internal gamma curve. Thereby, the signal processing unit 4 sequentially changes the luminance value due to the change in the gradation based on the corrected optical measurement signal supplied from the optical sensor 5 via the measurement value correcting unit 1. Gamma characteristics can be extracted. Therefore, the signal processing unit 4 adjusts a preset gamma curve corresponding to the gamma characteristic of the display panel 2 obtained from the optical measurement value.
When adjusting the gamma curve, the above-described gamma curve is used not only for an input video signal supplied from an external device but also for an internal video signal that is a video signal generated and output by the signal processing unit 4. A configuration may be adopted in which the processing given to the display panel 2 is performed without correction, the processing for extracting the gamma characteristic is performed, and the gamma curve is adjusted.
As described above, the signal processing unit 4 is set to perform measurement of the optical measurement value as data for adjusting the setting value of the image quality control setting value in the order in which the timing signals are output. Therefore, the signal processing unit 4 sequentially supplies the corrected optical measurement values from the measurement value correction unit 1 in this order, and as data for adjusting any control value in the set value group of image quality control set values. Can determine if it is an optical measurement

Next, FIG. 2 is a block diagram showing a configuration example of the measured value correction unit 1 in FIG. The measurement value correction unit 1 in this embodiment includes a measurement value acquisition unit 11, a coefficient calculation unit 12, a timer unit 13, a control unit 14, a correction calculation unit 15, a measurement value storage unit 16, and a correction value storage unit 17. .

When the adjustment start signal is supplied from the signal processing unit 4, the timer unit 13 resets the count value and then starts time counting processing.
When the adjustment start signal is supplied from the signal processing unit 4, the measurement value acquisition unit 11 sets the optical measurement value output from the optical sensor 5 as the first reference optical measurement value, and the first reference optical measurement value and the timer The time T0 that is the count value of the unit 13 (for example, the count value of the timer unit 13 is 0) is written as a set (that is, associated) and stored in the reference value storage area in the measurement value storage unit 16. The first reference optical measurement value needs to be an optical measurement value in which the signal processing unit 4 has enabled the luminance stabilization function and is controlled to the set luminance value.

Moreover, the measurement value acquisition part 11 reads the optical measurement value which the optical sensor 5 outputs, whenever the timing signal which acquires an optical measurement value is input.
At this time, the measurement value acquisition unit 11 reads the time Tn output from the timer unit 13 when the optical measurement value is read.
Then, the measurement value acquisition unit 11 combines identification information (for example, a number) indicating the order in which the timing signals are input, the optical measurement value, and the time Tn output by the timer unit 13 when the optical measurement value is acquired. As described above, the target optical measurement value storage area of the measurement value storage unit 16 is written and stored.

In addition, when the adjustment end signal is supplied from the signal processing unit 4, the measurement value acquisition unit 11 measures the optical measurement value at the time when the adjustment end signal is supplied, and uses the optical measurement value as the second reference optical measurement. Value. At this time, the measurement value acquisition unit 11 reads the time Ts output from the timer unit 13 at the time when the second reference optical measurement value is acquired.
Then, the measurement value acquisition unit 11 writes the second reference optical measurement value and the time Ts as a set to the reference value storage area of the measurement value storage unit 16, and indicates that the acquisition of the optical measurement value is completed. An end signal is output to the coefficient calculation unit 12.

The coefficient calculation unit 12 is measured from the reference value storage area of the measurement value storage unit 16 at the first reference optical measurement value L0 measured at the start time of the invalid period at time T0 and at the end time of the invalid period at time T1. The second reference optical measurement value L1 is read out together with the measured times T0 and T1.
Then, the coefficient calculator 12 subtracts the first reference optical measurement value L0 from the second reference optical measurement value L1, and the first reference optical measurement value L0 from the time T1 when the second reference optical measurement value L1 is measured. The coefficient α is calculated by subtracting the measured time T0 from the subtraction result.

In addition, when the luminance stability function is invalid, the coefficient calculation unit 12 is a function indicating a reference luminance value measured at a certain time, using the time width that has elapsed since the time when the luminance stability function was invalidated, that is, The linear function (linear function) shown in the equation (1) is obtained. That is, the coefficient calculation unit 12 multiplies the coefficient α (amount of change in optical measurement value) by a time variable, and adds the first reference optical measurement value L0 to the multiplication result as a linear function (1) below. Find the expression.
L = L0 + α (Tn−T0) (1)
In this equation (1),
α = (L1−L0) / (T1−T0)
Tn is the time when the optical measurement value to be corrected is measured.
Then, the coefficient calculation unit 12 outputs the function shown in the obtained equation (1) to the correction calculation unit 15.

Next, FIG. 3 is a graph showing a linear function generated by the coefficient calculation unit 12 in the present embodiment. In FIG. 3, the horizontal axis indicates time, and the vertical axis indicates the luminance value L. It can be seen that the function (1) is a linear function with the slope of the vertical axis of the luminance field L0 and an inclination of α.

Returning to FIG. 2, when the above function is supplied from the coefficient calculation unit 12, the correction calculation unit 15 sets the correction target optical measurement value stored in the target optical measurement value storage area of the measurement value storage unit 16 at time T0. Data are read and corrected from the nearest time, that is, in ascending order of identification information.
At this time, every time the correction target optical measurement value is read, the correction calculation unit 15 substitutes the time Ta at which the correction target optical measurement value is measured into Tn of the equation (1), and as shown in FIG. An estimated reference optical measurement value La at Ta is calculated. Then, the correction calculation unit 15 divides the first reference optical measurement value L0 by the calculated estimated reference optical measurement value La, and sets the division result as a change ratio β.

Then, the correction calculation unit 15 multiplies the calculated change ratio β by the optical measurement value that is the correction target optical measurement value, and calculates the multiplication result as the corrected optical measurement value of the optical measurement value measured at the time Ta. . Here, by multiplying the optical measurement value by the change ratio β, the optical measurement value at time Tn is optical measurement corresponding to the first reference luminance value L0 at time T0, that is, when the luminance stabilization function is effective. Will be converted to a value.
The correction calculation unit 15 sequentially writes the calculated corrected optical measurement values in the correction value storage unit 17 in correspondence with the identification numbers (numbers indicating the order) of the corresponding optical measurement values.

Next, FIG. 4 is a graph for explaining processing for sequentially calculating estimated optical measurement values from the linear function generated by the coefficient calculation unit 12 in the present embodiment. In FIG. 4, the horizontal axis indicates time, and the vertical axis indicates the luminance value L.
As shown in FIG. 4, the correction calculation unit 15 calculates estimated optical measurement values in the order of the times Ta and Tb using the equation (1), and calculates the change ratios βa and βb at the respective times. Then, the correction calculation unit 15 multiplies each of the change ratios βa and βb by the optical measurement value measured at the time corresponding to the change ratios βa and βb, and corrects the optical measurement value of the optical measurement value at each time. Is calculated.

Then, when the correction calculation unit 15 calculates the corrected optical measurement values for all the target optical measurement values stored in the target optical measurement value storage area of the measurement value storage unit 16, the correction processing of the optical measurement values ends. A processing end signal indicating that the processing has been performed is output to the control unit 14.
When the process end signal is supplied from the correction calculation unit 15, the control unit 14 ends the correction process of the acquired optical measurement value, and transmits a transmittable signal indicating that the obtained corrected optical measurement value can be transmitted. And transmitted to the signal processing unit 4.

The signal processing unit 4 indicates that, when a transmittable signal is supplied from the measurement value correcting unit 1, the mode shifts to a mode in which each image quality control setting value is adjusted, and then requests transmission of the corrected optical measurement value. A transmission request signal is transmitted to the measurement value correction unit 1.
When this transmission request signal is supplied, the control unit 14 reads out the corrected optical measurement values stored in the correction value storage unit 17 for each identification number, for example, the order of the stored numbers (that is, when measuring) The read correction optical measurement values are sequentially output to the signal processing unit 4 together with the order numbers of the timing signals.

Here, the signal processing unit 4 stores a correspondence table that associates the order of the timing signals with the control value identification number indicating which control value in the set value group of the image quality control setting values in the internal storage unit within itself. Has been.
Therefore, the signal processing unit 4 writes and stores the corrected optical measurement value supplied from the measurement value correction unit 1 in the correspondence table in correspondence with the order of the timing signals.

Then, when adjusting each of the control values in the set value group of image quality setting values, the signal processing unit 4 reads out the corrected optical setting value corresponding to the identification number of each control value from the correspondence table, and sets the corresponding control value. Perform the adjustment process.
For example, when adjusting the gamma curve, the signal processing unit 4 stops the gamma correction function to disable gamma correction, and then linearly adjusts the gradation of halftones every time a timing signal is output. The brightness adjustment signal increased to 1 is output to the display panel 2.

Then, the signal processing unit 4 determines which correction optical measurement value is a measurement value for measuring the gamma characteristic according to the order number of the correction optical measurement value supplied from the measurement value correction unit 1 and which gradation. It is determined whether the measured value corresponds to the value, the set gradation value is compared with the luminance value indicated by the corrected optical measured value, and the gamma characteristic of the display panel 2 is obtained. The signal processing unit 4 calculates a gamma curve for correcting the gamma characteristic based on the gamma characteristic obtained from the corrected optical measurement value, and sets it as a control value in the new image quality control setting value. Then, after the gamma curve adjustment process is completed, the signal processing unit 4 validates the gamma correction process.

For example, when adjusting the black luminance, the signal processing unit 4 outputs the gradation to the display panel 2 as the lowest value when outputting the timing signal.
Then, the signal processing unit 4 performs correction for adjusting the black luminance from the corrected optical measurement values supplied from the measurement value correction unit 1 based on the order number of the correction optical measurement values supplied from the measurement value correction unit 1. An optical measurement value is determined, and a luminance value indicated by the corrected optical measurement value is compared with a preset luminance value of black luminance to obtain a control value of the liquid crystal element that becomes a preset luminance value.

At this time, each time the control value is changed, the signal processing unit 4 transmits a timing signal to the measurement value correcting unit 1 to obtain a control value that is a luminance value within a preset range. Like the control value of the brightness value of the black brightness, the brightness value by the adjusted control value is measured, and it is determined whether or not this brightness value is included in the preset brightness value range, and the final control is performed. In the case of iterative processing in which adjustment for obtaining values is performed, the signal processing unit 4 may be configured to have an adjustment mode for only this iterative processing.

As described above, in the present embodiment, the white luminance is set so as to correspond to the luminance value of the white luminance at the time when the luminance stabilizing function is disabled (that is, when the luminance stabilizing function is enabled), that is, in the luminance stable state. The optical measurement value after a lapse of time can be corrected so as to correspond to the luminance value of
Thus, according to the present embodiment, after invalidating the luminance stabilization function, the influence of the luminance value emitted from the light source that changes with time is eliminated, and the image quality control setting value in the state where the luminance stabilization function is working Adjustments can be made and display quality can be maintained.

FIG. 5 shows a corrected optical measurement value using three reference measurement values: a first reference measurement value (time T0), a second reference measurement value (time T1), and a third reference measurement value (time T2). It is a graph explaining the process which calculates.
In the description of the above-described embodiment, the process of correcting the optical measurement value to the correction optical value is performed based on the change amount of the luminance value per unit time obtained from the two reference measurement values at time T0 and time T1. Yes.

However, if the time during which the luminance value stabilization function is disabled becomes long, in the case of two-point measurement, it is considered that the error of the corrected optical measurement value increases if linear correction between the two points is performed.
For this reason, as shown in FIG. 5, according to the time width during which the luminance stabilization function is disabled, the luminance values of white luminance are measured at a plurality of reference measurement values of three or more points, and the plurality of reference measurement values are obtained. It is good also as a structure which performs the used correction | amendment.

For example, as shown in FIG. 5, the first reference measurement value L0 at time T0, the second reference measurement value L1 at time T1, and the third reference measurement value T2 at time T2 are used.
Returning to FIG. 1, the coefficient calculation unit 12 indicates linearity between the first reference measurement value L0 and the third reference measurement value, which is used for correcting the optical measurement value measured between the time T0 and the time T2. The following equation (2) is obtained.
L = L0 + α (Tn−T0) (2)
In this equation (2),
α = (L2−L0) / (T2−T0)
Tn is the time when the optical measurement value to be corrected is measured.
And the correction | amendment calculating part 15 calculates | requires change ratio (beta) from this (2) Formula, and calculates | requires each correction | amendment optical measurement value of the optical measurement value measured between the time T0 and the time T2.
That is, the correction calculation unit 15 substitutes the time Ta for the time Tn in the equation (2), and calculates the estimated reference optical measurement value La at the time Ta. Then, the correction calculation unit 15 divides the first reference measurement value L0 by the estimated reference optical measurement value La and multiplies the optical measurement value measured at time Ta by the coefficient β to calculate the correction optical measurement value. To do.

In addition, the coefficient calculation unit 12 indicates linearity between the first reference measurement value L0 and the third reference measurement value used for correcting the optical measurement value measured between the time T2 and the time T1 ( 3) Find the equation.
L = L2 + α (Tn−T2) (3)
In this equation (3),
α = (L1−L2) / (T1−T2)
Tn is the time when the optical measurement value to be corrected is measured.
And the correction | amendment calculating part 15 calculates | requires change ratio (beta) from this (3) Formula, and calculates | requires each correction | amendment optical measurement value of the optical measurement value measured between the time T2 and the time T1.
That is, the correction calculation unit 15 substitutes the time Tb for the time Tn in the equation (3), and calculates the estimated reference optical measurement value Lb at the time Tb. Then, the correction calculation unit 15 divides the third reference measurement value L2 by the calculated estimated reference optical measurement value Lb, and multiplies the optical measurement value measured at time Tb by the coefficient β to calculate the correction optical measurement value. To do.

As described above, a plurality of reference measurement values are measured in a time width in which the luminance stabilization function is disabled, and a linear function is obtained at each time between adjacent reference measurement values. A corrected optical measurement value with higher accuracy can be obtained by correcting the optical measurement value between the respective reference measurement values in correspondence with each of the linear functions.

Also, as shown in FIG. 5, when measuring three or more reference measurement values, instead of obtaining a linear function between the reference measurement values, the change in the actual white luminance value is changed from each reference measurement value. A configuration for generating a corresponding spline curve may be adopted. Then, by performing spline correction with the change ratio obtained from the generated spline curve, it is possible to perform correction with the optical measurement value as the corrected optical measurement value with higher accuracy.

Further, at time T2 in FIG. 5, that is, between the measurement of the optical measurement value, the measurement process of the optical measurement value is temporarily stopped, the luminance stabilization function is enabled, the white luminance value is stabilized, and then again. The signal processing unit 4 may be configured to disable the luminance stabilization function and restart the measurement process of the optical measurement value. This makes it possible to substantially reduce the time width over which the luminance stabilization function is disabled, such as when the amount of measurement of optical measurement values is large and the time width over which the luminance stability function is disabled becomes long. The amount of change can be further reduced, and the error in correcting the optical measurement value to the corrected optical measurement value can be reduced.

Although the reference measurement value used for correction is described as the luminance value of white luminance, any luminance value such as the luminance value of any color or the luminance value of black luminance is used instead of the luminance value of white luminance. May be.
In the embodiments, the liquid crystal display device has been described as an example. However, the present invention can be applied to any display device as long as the optical measurement value such as a luminance value varies with time.
Further, in order to adjust the image quality control setting value, the process of measuring the optical measurement value while disabling the luminance stabilization function is performed by the user inputting a command for adjusting the image quality control setting value to the display device 100 from an input device (not shown). Or a configuration in which the signal processing unit 4 is activated each time a preset time elapses after the display device 100 is turned on, or a configuration including both.

When used as a display device (for example, a liquid crystal display device) for industrial fields such as computer graphics and medical applications that are used in applications that require high-precision color reproduction, the display image display quality for the user over a long period of time Thus, it is possible to maintain stability.

DESCRIPTION OF SYMBOLS 1 Measurement value correction | amendment part 2 Display panel 3 Backlight 4 Signal processing part 5 Optical sensor 11 Measurement value acquisition part 12 Coefficient calculation part 13 Timer part 14 Control part 15 Correction calculation part 16 Measurement value memory | storage part 17 Correction value memory | storage part 21 Measurement area | region 100 Display device

Claims

A display panel for displaying images,
An optical sensor that is disposed opposite to the display surface of the display panel and measures the amount of light emitted from the display panel as an optical measurement value;
A measurement value correction unit that corrects an optical measurement value to be corrected, which is an optical measurement value to be corrected, by a function indicating a change amount of the optical measurement value per unit time, and outputs the corrected optical measurement value;
A control value for controlling the display panel, which stabilizes the display quality of the image displayed on the display panel, is generated from the corrected optical measurement value, and from this control value and an input video signal supplied from an external device A signal processing unit for generating a processed video signal for displaying the image,
The function indicates a change in the irradiation amount during an invalid period in which the signal processing unit disables a stable function of making the irradiation amount of the light source of the front display panel constant when measuring the optical measurement value to be corrected. A display device.
The measurement value correction unit
A timer unit for counting time;
A plurality of reference optical measurement values measured at different times including the start time at which the invalid period is started, and a coefficient calculation unit for obtaining a function indicating a relationship between the time when the timer unit measures each of the reference optical measurement values; ,
When obtaining the corrected optical measurement value from the correction target optical measurement value, an estimated reference optical measurement value at the time when the correction target optical measurement value is measured is obtained from the function, and the reference at the start time is determined by the estimated reference optical measurement value. A correction operation unit that divides an optical measurement value, sets the division result as a change ratio, multiplies the change ratio by the optical measurement value to be corrected, and sets the result of the multiplication as a correction optical measurement value. The display device according to claim 1.
The coefficient calculator is
A first reference optical measurement value that is an optical measurement value measured at a first time that is the start time counted by the timer, and an optical that is measured at a second time after the first time counted by the timer. Find the difference from the second reference optical measurement value that is the measurement value, subtract the difference by the time width of the difference between the first time and the second time, calculate the optical measurement value change amount per unit time, 3. A linear function obtained by multiplying an optical measurement value change amount by a time variable, adding the first reference optical measurement value to the multiplication result, and using the linear function as the function. The display device described in 1.
The coefficient calculator is
The spline curve is obtained from a plurality of reference optical measurement values measured at different times including the reference optical measurement value measured at the start time, and the spline curve is used as the function. Display device.
The display device according to any one of claims 1 to 4, wherein a luminance value measured as the reference optical measurement value is white luminance.
6. The display device according to claim 1, wherein the optical measurement value to be corrected is a luminance value in each of black luminance, gamma characteristic, and color measurement.
A process of measuring an irradiation amount of light emitted from the display panel by an optical sensor as an optical measurement value, which is disposed opposite to the display surface of the display panel of the liquid crystal display device,
A measurement value correction process in which the measurement value correction unit corrects an optical measurement value to be corrected, which is an optical measurement value to be corrected, with a function indicating a change amount of the optical measurement value per unit time, and outputs the corrected optical measurement value. When,
A signal processing unit generates a control value for controlling the display panel, which stabilizes the display quality of the image displayed on the display panel, based on the corrected optical measurement value, and is supplied from the control value and an external device. A signal processing step of generating a post-processing video signal for displaying an image on the display panel from an input video signal,
The function indicates a change in the irradiation amount during an invalid period in which the signal processing unit disables a stable function of making the irradiation amount of the light source of the front display panel constant when measuring the optical measurement value to be corrected. Display characteristic calibration method characterized by